Include type declaration SourceAnn for values

[purefunctor]

Description of the change

This allows the compiler to be more honest about the source annotation for value declarations. During desugaring, the SourceAnn for a value declaration is replaced with a corresponding type declaration's SourceAnn if it exists.

I noticed this while working on #4247 and it messes up the order for constructing the interval tree
which I intend to serialize into a file/use in psc-ide as part of the type-on-hover stuff.

Another solution for this is to expand the annotation during desugaring such that both the annotation and value declaration is covered, but this changes behaviour in error messages.

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Checklist:

• Added a file to CHANGELOG.d for this PR (see CHANGELOG.d/README.md)
• Added myself to CONTRIBUTORS.md (if this is my first contribution)
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)